// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/pipe.c
 *
 *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
 */

#include <generated/deconfig.h>
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/log2.h>
#include <linux/mount.h>
#include <linux/pseudo_fs.h>
#include <linux/magic.h>
#include <linux/pipe_fs_i.h>
#include <linux/uio.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/audit.h>
#include <linux/syscalls.h>
#include <linux/fcntl.h>
#include <linux/memcontrol.h>
#include <linux/watch_queue.h>

#include <linux/uaccess.h>
#include <asm/ioctls.h>

#include "internal.h"

///*
// * The max size that a non-root user is allowed to grow the pipe. Can
// * be set by root in /proc/sys/fs/pipe-max-size
// */
//unsigned int pipe_max_size = 1048576;

///* Maximum allocatable pages per user. Hard limit is unset by default, soft
// * matches default values.
// */
//unsigned long pipe_user_pages_hard;
//unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;

///*
// * We use head and tail indices that aren't masked off, except at the point of
// * dereference, but rather they're allowed to wrap naturally.  This means there
// * isn't a dead spot in the buffer, but the ring has to be a power of two and
// * <= 2^31.
// * -- David Howells 2019-09-23.
// *
// * Reads with count = 0 should always return 0.
// * -- Julian Bradfield 1999-06-07.
// *
// * FIFOs and Pipes now generate SIGIO for both readers and writers.
// * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
// *
// * pipe_read & write cleanup
// * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
// */

//static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
//{
//	if (pipe->files)
//		mutex_lock_nested(&pipe->mutex, subclass);
//}

//void pipe_lock(struct pipe_inode_info *pipe)
//{
//	/*
//	 * pipe_lock() nests non-pipe inode locks (for writing to a file)
//	 */
//	pipe_lock_nested(pipe, I_MUTEX_PARENT);
//}
//EXPORT_SYMBOL(pipe_lock);

//void pipe_unlock(struct pipe_inode_info *pipe)
//{
//	if (pipe->files)
//		mutex_unlock(&pipe->mutex);
//}
//EXPORT_SYMBOL(pipe_unlock);

//static inline void __pipe_lock(struct pipe_inode_info *pipe)
//{
//	mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
//}

//static inline void __pipe_unlock(struct pipe_inode_info *pipe)
//{
//	mutex_unlock(&pipe->mutex);
//}

//void pipe_double_lock(struct pipe_inode_info *pipe1,
//		      struct pipe_inode_info *pipe2)
//{
//	BUG_ON(pipe1 == pipe2);

//	if (pipe1 < pipe2) {
//		pipe_lock_nested(pipe1, I_MUTEX_PARENT);
//		pipe_lock_nested(pipe2, I_MUTEX_CHILD);
//	} else {
//		pipe_lock_nested(pipe2, I_MUTEX_PARENT);
//		pipe_lock_nested(pipe1, I_MUTEX_CHILD);
//	}
//}

//static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
//				  struct pipe_buffer *buf)
//{
//	struct page *page = buf->page;

//	/*
//	 * If nobody else uses this page, and we don't already have a
//	 * temporary page, let's keep track of it as a one-deep
//	 * allocation cache. (Otherwise just release our reference to it)
//	 */
//	if (page_count(page) == 1 && !pipe->tmp_page)
//		pipe->tmp_page = page;
//	else
//		put_page(page);
//}

//static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
//		struct pipe_buffer *buf)
//{
//	struct page *page = buf->page;

//	if (page_count(page) != 1)
//		return false;
//	memcg_kmem_uncharge_page(page, 0);
//	__SetPageLocked(page);
//	return true;
//}

/**
 * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
 * @pipe:	the pipe that the buffer belongs to
 * @buf:	the buffer to attempt to steal
 *
 * Description:
 *	This function attempts to steal the &struct page attached to
 *	@buf. If successful, this function returns 0 and returns with
 *	the page locked. The caller may then reuse the page for whatever
 *	he wishes; the typical use is insertion into a different file
 *	page cache.
 */
bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
		struct pipe_buffer *buf)
{
	struct page *page = buf->page;

	/*
	 * A reference of one is golden, that means that the owner of this
	 * page is the only one holding a reference to it. lock the page
	 * and return OK.
	 */
	if (page_count(page) == 1) {
		lock_page(page);
		return true;
	}
	return false;
}
EXPORT_SYMBOL(generic_pipe_buf_try_steal);

/**
 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 * @pipe:	the pipe that the buffer belongs to
 * @buf:	the buffer to get a reference to
 *
 * Description:
 *	This function grabs an extra reference to @buf. It's used in
 *	in the tee() system call, when we duplicate the buffers in one
 *	pipe into another.
 */
bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
{
	return try_get_page(buf->page);
}
EXPORT_SYMBOL(generic_pipe_buf_get);

/**
 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 * @pipe:	the pipe that the buffer belongs to
 * @buf:	the buffer to put a reference to
 *
 * Description:
 *	This function releases a reference to @buf.
 */
void generic_pipe_buf_release(struct pipe_inode_info *pipe,
			      struct pipe_buffer *buf)
{
	put_page(buf->page);
}
EXPORT_SYMBOL(generic_pipe_buf_release);

//static const struct pipe_buf_operations anon_pipe_buf_ops = {
//	.release	= anon_pipe_buf_release,
//	.try_steal	= anon_pipe_buf_try_steal,
//	.get		= generic_pipe_buf_get,
//};

///* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
//static inline bool pipe_readable(const struct pipe_inode_info *pipe)
//{
//	unsigned int head = READ_ONCE(pipe->head);
//	unsigned int tail = READ_ONCE(pipe->tail);
//	unsigned int writers = READ_ONCE(pipe->writers);

//	return !pipe_empty(head, tail) || !writers;
//}

//static ssize_t
//pipe_read(struct kiocb *iocb, struct iov_iter *to)
//{
//	size_t total_len = iov_iter_count(to);
//	struct file *filp = iocb->ki_filp;
//	struct pipe_inode_info *pipe = filp->private_data;
//	bool was_full, wake_next_reader = false;
//	ssize_t ret;

//	/* Null read succeeds. */
//	if (unlikely(total_len == 0))
//		return 0;

//	ret = 0;
//	__pipe_lock(pipe);

//	/*
//	 * We only wake up writers if the pipe was full when we started
//	 * reading in order to avoid unnecessary wakeups.
//	 *
//	 * But when we do wake up writers, we do so using a sync wakeup
//	 * (WF_SYNC), because we want them to get going and generate more
//	 * data for us.
//	 */
//	was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
//	for (;;) {
//		unsigned int head = pipe->head;
//		unsigned int tail = pipe->tail;
//		unsigned int mask = pipe->ring_size - 1;

//#ifdef CONFIG_WATCH_QUEUE
//		if (pipe->note_loss) {
//			struct watch_notification n;

//			if (total_len < 8) {
//				if (ret == 0)
//					ret = -ENOBUFS;
//				break;
//			}

//			n.type = WATCH_TYPE_META;
//			n.subtype = WATCH_META_LOSS_NOTIFICATION;
//			n.info = watch_sizeof(n);
//			if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
//				if (ret == 0)
//					ret = -EFAULT;
//				break;
//			}
//			ret += sizeof(n);
//			total_len -= sizeof(n);
//			pipe->note_loss = false;
//		}
//#endif

//		if (!pipe_empty(head, tail)) {
//			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
//			size_t chars = buf->len;
//			size_t written;
//			int error;

//			if (chars > total_len) {
//				if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
//					if (ret == 0)
//						ret = -ENOBUFS;
//					break;
//				}
//				chars = total_len;
//			}

//			error = pipe_buf_confirm(pipe, buf);
//			if (error) {
//				if (!ret)
//					ret = error;
//				break;
//			}

//			written = copy_page_to_iter(buf->page, buf->offset, chars, to);
//			if (unlikely(written < chars)) {
//				if (!ret)
//					ret = -EFAULT;
//				break;
//			}
//			ret += chars;
//			buf->offset += chars;
//			buf->len -= chars;

//			/* Was it a packet buffer? Clean up and exit */
//			if (buf->flags & PIPE_BUF_FLAG_PACKET) {
//				total_len = chars;
//				buf->len = 0;
//			}

//			if (!buf->len) {
//				pipe_buf_release(pipe, buf);
//				spin_lock_irq(&pipe->rd_wait.lock);
//#ifdef CONFIG_WATCH_QUEUE
//				if (buf->flags & PIPE_BUF_FLAG_LOSS)
//					pipe->note_loss = true;
//#endif
//				tail++;
//				pipe->tail = tail;
//				spin_unlock_irq(&pipe->rd_wait.lock);
//			}
//			total_len -= chars;
//			if (!total_len)
//				break;	/* common path: read succeeded */
//			if (!pipe_empty(head, tail))	/* More to do? */
//				continue;
//		}

//		if (!pipe->writers)
//			break;
//		if (ret)
//			break;
//		if (filp->f_flags & O_NONBLOCK) {
//			ret = -EAGAIN;
//			break;
//		}
//		__pipe_unlock(pipe);

//		/*
//		 * We only get here if we didn't actually read anything.
//		 *
//		 * However, we could have seen (and removed) a zero-sized
//		 * pipe buffer, and might have made space in the buffers
//		 * that way.
//		 *
//		 * You can't make zero-sized pipe buffers by doing an empty
//		 * write (not even in packet mode), but they can happen if
//		 * the writer gets an EFAULT when trying to fill a buffer
//		 * that already got allocated and inserted in the buffer
//		 * array.
//		 *
//		 * So we still need to wake up any pending writers in the
//		 * _very_ unlikely case that the pipe was full, but we got
//		 * no data.
//		 */
//		if (unlikely(was_full)) {
//			wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
//			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
//		}

//		/*
//		 * But because we didn't read anything, at this point we can
//		 * just return directly with -ERESTARTSYS if we're interrupted,
//		 * since we've done any required wakeups and there's no need
//		 * to mark anything accessed. And we've dropped the lock.
//		 */
//		if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
//			return -ERESTARTSYS;

//		__pipe_lock(pipe);
//		was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
//		wake_next_reader = true;
//	}
//	if (pipe_empty(pipe->head, pipe->tail))
//		wake_next_reader = false;
//	__pipe_unlock(pipe);

//	if (was_full) {
//		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
//		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
//	}
//	if (wake_next_reader)
//		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
//	if (ret > 0)
//		file_accessed(filp);
//	return ret;
//}

//static inline int is_packetized(struct file *file)
//{
//	return (file->f_flags & O_DIRECT) != 0;
//}

///* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
//static inline bool pipe_writable(const struct pipe_inode_info *pipe)
//{
//	unsigned int head = READ_ONCE(pipe->head);
//	unsigned int tail = READ_ONCE(pipe->tail);
//	unsigned int max_usage = READ_ONCE(pipe->max_usage);

//	return !pipe_full(head, tail, max_usage) ||
//		!READ_ONCE(pipe->readers);
//}

//static ssize_t
//pipe_write(struct kiocb *iocb, struct iov_iter *from)
//{
//	struct file *filp = iocb->ki_filp;
//	struct pipe_inode_info *pipe = filp->private_data;
//	unsigned int head;
//	ssize_t ret = 0;
//	size_t total_len = iov_iter_count(from);
//	ssize_t chars;
//	bool was_empty = false;
//	bool wake_next_writer = false;

//	/* Null write succeeds. */
//	if (unlikely(total_len == 0))
//		return 0;

//	__pipe_lock(pipe);

//	if (!pipe->readers) {
//		send_sig(SIGPIPE, current, 0);
//		ret = -EPIPE;
//		goto out;
//	}

//#ifdef CONFIG_WATCH_QUEUE
//	if (pipe->watch_queue) {
//		ret = -EXDEV;
//		goto out;
//	}
//#endif

//	/*
//	 * Only wake up if the pipe started out empty, since
//	 * otherwise there should be no readers waiting.
//	 *
//	 * If it wasn't empty we try to merge new data into
//	 * the last buffer.
//	 *
//	 * That naturally merges small writes, but it also
//	 * page-aligs the rest of the writes for large writes
//	 * spanning multiple pages.
//	 */
//	head = pipe->head;
//	was_empty = pipe_empty(head, pipe->tail);
//	chars = total_len & (PAGE_SIZE-1);
//	if (chars && !was_empty) {
//		unsigned int mask = pipe->ring_size - 1;
//		struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
//		int offset = buf->offset + buf->len;

//		if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
//		    offset + chars <= PAGE_SIZE) {
//			ret = pipe_buf_confirm(pipe, buf);
//			if (ret)
//				goto out;

//			ret = copy_page_from_iter(buf->page, offset, chars, from);
//			if (unlikely(ret < chars)) {
//				ret = -EFAULT;
//				goto out;
//			}

//			buf->len += ret;
//			if (!iov_iter_count(from))
//				goto out;
//		}
//	}

//	for (;;) {
//		if (!pipe->readers) {
//			send_sig(SIGPIPE, current, 0);
//			if (!ret)
//				ret = -EPIPE;
//			break;
//		}

//		head = pipe->head;
//		if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
//			unsigned int mask = pipe->ring_size - 1;
//			struct pipe_buffer *buf = &pipe->bufs[head & mask];
//			struct page *page = pipe->tmp_page;
//			int copied;

//			if (!page) {
//				page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
//				if (unlikely(!page)) {
//					ret = ret ? : -ENOMEM;
//					break;
//				}
//				pipe->tmp_page = page;
//			}

//			/* Allocate a slot in the ring in advance and attach an
//			 * empty buffer.  If we fault or otherwise fail to use
//			 * it, either the reader will consume it or it'll still
//			 * be there for the next write.
//			 */
//			spin_lock_irq(&pipe->rd_wait.lock);

//			head = pipe->head;
//			if (pipe_full(head, pipe->tail, pipe->max_usage)) {
//				spin_unlock_irq(&pipe->rd_wait.lock);
//				continue;
//			}

//			pipe->head = head + 1;
//			spin_unlock_irq(&pipe->rd_wait.lock);

//			/* Insert it into the buffer array */
//			buf = &pipe->bufs[head & mask];
//			buf->page = page;
//			buf->ops = &anon_pipe_buf_ops;
//			buf->offset = 0;
//			buf->len = 0;
//			if (is_packetized(filp))
//				buf->flags = PIPE_BUF_FLAG_PACKET;
//			else
//				buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
//			pipe->tmp_page = NULL;

//			copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
//			if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
//				if (!ret)
//					ret = -EFAULT;
//				break;
//			}
//			ret += copied;
//			buf->offset = 0;
//			buf->len = copied;

//			if (!iov_iter_count(from))
//				break;
//		}

//		if (!pipe_full(head, pipe->tail, pipe->max_usage))
//			continue;

//		/* Wait for buffer space to become available. */
//		if (filp->f_flags & O_NONBLOCK) {
//			if (!ret)
//				ret = -EAGAIN;
//			break;
//		}
//		if (signal_pending(current)) {
//			if (!ret)
//				ret = -ERESTARTSYS;
//			break;
//		}

//		/*
//		 * We're going to release the pipe lock and wait for more
//		 * space. We wake up any readers if necessary, and then
//		 * after waiting we need to re-check whether the pipe
//		 * become empty while we dropped the lock.
//		 */
//		__pipe_unlock(pipe);
//		if (was_empty) {
//			wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
//			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
//		}
//		wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
//		__pipe_lock(pipe);
//		was_empty = pipe_empty(pipe->head, pipe->tail);
//		wake_next_writer = true;
//	}
//out:
//	if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
//		wake_next_writer = false;
//	__pipe_unlock(pipe);

//	/*
//	 * If we do do a wakeup event, we do a 'sync' wakeup, because we
//	 * want the reader to start processing things asap, rather than
//	 * leave the data pending.
//	 *
//	 * This is particularly important for small writes, because of
//	 * how (for example) the GNU make jobserver uses small writes to
//	 * wake up pending jobs
//	 */
//	if (was_empty) {
//		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
//		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
//	}
//	if (wake_next_writer)
//		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
//	if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
//		int err = file_update_time(filp);
//		if (err)
//			ret = err;
//		sb_end_write(file_inode(filp)->i_sb);
//	}
//	return ret;
//}

//static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
//{
//	struct pipe_inode_info *pipe = filp->private_data;
//	int count, head, tail, mask;

//	switch (cmd) {
//	case FIONREAD:
//		__pipe_lock(pipe);
//		count = 0;
//		head = pipe->head;
//		tail = pipe->tail;
//		mask = pipe->ring_size - 1;

//		while (tail != head) {
//			count += pipe->bufs[tail & mask].len;
//			tail++;
//		}
//		__pipe_unlock(pipe);

//		return put_user(count, (int __user *)arg);

//#ifdef CONFIG_WATCH_QUEUE
//	case IOC_WATCH_QUEUE_SET_SIZE: {
//		int ret;
//		__pipe_lock(pipe);
//		ret = watch_queue_set_size(pipe, arg);
//		__pipe_unlock(pipe);
//		return ret;
//	}

//	case IOC_WATCH_QUEUE_SET_FILTER:
//		return watch_queue_set_filter(
//			pipe, (struct watch_notification_filter __user *)arg);
//#endif

//	default:
//		return -ENOIOCTLCMD;
//	}
//}

///* No kernel lock held - fine */
//static __poll_t
//pipe_poll(struct file *filp, poll_table *wait)
//{
//	__poll_t mask;
//	struct pipe_inode_info *pipe = filp->private_data;
//	unsigned int head, tail;

//	/*
//	 * Reading pipe state only -- no need for acquiring the semaphore.
//	 *
//	 * But because this is racy, the code has to add the
//	 * entry to the poll table _first_ ..
//	 */
//	if (filp->f_mode & FMODE_READ)
//		poll_wait(filp, &pipe->rd_wait, wait);
//	if (filp->f_mode & FMODE_WRITE)
//		poll_wait(filp, &pipe->wr_wait, wait);

//	/*
//	 * .. and only then can you do the racy tests. That way,
//	 * if something changes and you got it wrong, the poll
//	 * table entry will wake you up and fix it.
//	 */
//	head = READ_ONCE(pipe->head);
//	tail = READ_ONCE(pipe->tail);

//	mask = 0;
//	if (filp->f_mode & FMODE_READ) {
//		if (!pipe_empty(head, tail))
//			mask |= EPOLLIN | EPOLLRDNORM;
//		if (!pipe->writers && filp->f_version != pipe->w_counter)
//			mask |= EPOLLHUP;
//	}

//	if (filp->f_mode & FMODE_WRITE) {
//		if (!pipe_full(head, tail, pipe->max_usage))
//			mask |= EPOLLOUT | EPOLLWRNORM;
//		/*
//		 * Most Unices do not set EPOLLERR for FIFOs but on Linux they
//		 * behave exactly like pipes for poll().
//		 */
//		if (!pipe->readers)
//			mask |= EPOLLERR;
//	}

//	return mask;
//}

//static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
//{
//	int kill = 0;

//	spin_lock(&inode->i_lock);
//	if (!--pipe->files) {
//		inode->i_pipe = NULL;
//		kill = 1;
//	}
//	spin_unlock(&inode->i_lock);

//	if (kill)
//		free_pipe_info(pipe);
//}

//static int
//pipe_release(struct inode *inode, struct file *file)
//{
//	struct pipe_inode_info *pipe = file->private_data;

//	__pipe_lock(pipe);
//	if (file->f_mode & FMODE_READ)
//		pipe->readers--;
//	if (file->f_mode & FMODE_WRITE)
//		pipe->writers--;

//	/* Was that the last reader or writer, but not the other side? */
//	if (!pipe->readers != !pipe->writers) {
//		wake_up_interruptible_all(&pipe->rd_wait);
//		wake_up_interruptible_all(&pipe->wr_wait);
//		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
//		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
//	}
//	__pipe_unlock(pipe);

//	put_pipe_info(inode, pipe);
//	return 0;
//}

//static int
//pipe_fasync(int fd, struct file *filp, int on)
//{
//	struct pipe_inode_info *pipe = filp->private_data;
//	int retval = 0;

//	__pipe_lock(pipe);
//	if (filp->f_mode & FMODE_READ)
//		retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
//	if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
//		retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
//		if (retval < 0 && (filp->f_mode & FMODE_READ))
//			/* this can happen only if on == T */
//			fasync_helper(-1, filp, 0, &pipe->fasync_readers);
//	}
//	__pipe_unlock(pipe);
//	return retval;
//}

//unsigned long account_pipe_buffers(struct user_struct *user,
//				   unsigned long old, unsigned long new)
//{
//	return atomic_long_add_return(new - old, &user->pipe_bufs);
//}

//bool too_many_pipe_buffers_soft(unsigned long user_bufs)
//{
//	unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);

//	return soft_limit && user_bufs > soft_limit;
//}

//bool too_many_pipe_buffers_hard(unsigned long user_bufs)
//{
//	unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);

//	return hard_limit && user_bufs > hard_limit;
//}

//bool pipe_is_unprivileged_user(void)
//{
//	return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
//}

//struct pipe_inode_info *alloc_pipe_info(void)
//{
//	struct pipe_inode_info *pipe;
//	unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
//	struct user_struct *user = get_current_user();
//	unsigned long user_bufs;
//	unsigned int max_size = READ_ONCE(pipe_max_size);

//	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
//	if (pipe == NULL)
//		goto out_free_uid;

//	if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
//		pipe_bufs = max_size >> PAGE_SHIFT;

//	user_bufs = account_pipe_buffers(user, 0, pipe_bufs);

//	if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
//		user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
//		pipe_bufs = 1;
//	}

//	if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
//		goto out_revert_acct;

//	pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
//			     GFP_KERNEL_ACCOUNT);

//	if (pipe->bufs) {
//		init_waitqueue_head(&pipe->rd_wait);
//		init_waitqueue_head(&pipe->wr_wait);
//		pipe->r_counter = pipe->w_counter = 1;
//		pipe->max_usage = pipe_bufs;
//		pipe->ring_size = pipe_bufs;
//		pipe->nr_accounted = pipe_bufs;
//		pipe->user = user;
//		mutex_init(&pipe->mutex);
//		return pipe;
//	}

//out_revert_acct:
//	(void) account_pipe_buffers(user, pipe_bufs, 0);
//	kfree(pipe);
//out_free_uid:
//	free_uid(user);
//	return NULL;
//}

//void free_pipe_info(struct pipe_inode_info *pipe)
//{
//	int i;

//#ifdef CONFIG_WATCH_QUEUE
//	if (pipe->watch_queue) {
//		watch_queue_clear(pipe->watch_queue);
//		put_watch_queue(pipe->watch_queue);
//	}
//#endif

//	(void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
//	free_uid(pipe->user);
//	for (i = 0; i < pipe->ring_size; i++) {
//		struct pipe_buffer *buf = pipe->bufs + i;
//		if (buf->ops)
//			pipe_buf_release(pipe, buf);
//	}
//	if (pipe->tmp_page)
//		__free_page(pipe->tmp_page);
//	kfree(pipe->bufs);
//	kfree(pipe);
//}

//static struct vfsmount *pipe_mnt __read_mostly;

///*
// * pipefs_dname() is called from d_path().
// */
//static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
//{
//	return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
//				d_inode(dentry)->i_ino);
//}

//static const struct dentry_operations pipefs_dentry_operations = {
//	.d_dname	= pipefs_dname,
//};

//static struct inode * get_pipe_inode(void)
//{
//	struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
//	struct pipe_inode_info *pipe;

//	if (!inode)
//		goto fail_inode;

//	inode->i_ino = get_next_ino();

//	pipe = alloc_pipe_info();
//	if (!pipe)
//		goto fail_iput;

//	inode->i_pipe = pipe;
//	pipe->files = 2;
//	pipe->readers = pipe->writers = 1;
//	inode->i_fop = &pipefifo_fops;

//	/*
//	 * Mark the inode dirty from the very beginning,
//	 * that way it will never be moved to the dirty
//	 * list because "mark_inode_dirty()" will think
//	 * that it already _is_ on the dirty list.
//	 */
//	inode->i_state = I_DIRTY;
//	inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
//	inode->i_uid = current_fsuid();
//	inode->i_gid = current_fsgid();
//	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);

//	return inode;

//fail_iput:
//	iput(inode);

//fail_inode:
//	return NULL;
//}

//int create_pipe_files(struct file **res, int flags)
//{
//	struct inode *inode = get_pipe_inode();
//	struct file *f;
//	int error;

//	if (!inode)
//		return -ENFILE;

//	if (flags & O_NOTIFICATION_PIPE) {
//		error = watch_queue_init(inode->i_pipe);
//		if (error) {
//			free_pipe_info(inode->i_pipe);
//			iput(inode);
//			return error;
//		}
//	}

//	f = alloc_file_pseudo(inode, pipe_mnt, "",
//				O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
//				&pipefifo_fops);
//	if (IS_ERR(f)) {
//		free_pipe_info(inode->i_pipe);
//		iput(inode);
//		return PTR_ERR(f);
//	}

//	f->private_data = inode->i_pipe;

//	res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
//				  &pipefifo_fops);
//	if (IS_ERR(res[0])) {
//		put_pipe_info(inode, inode->i_pipe);
//		fput(f);
//		return PTR_ERR(res[0]);
//	}
//	res[0]->private_data = inode->i_pipe;
//	res[1] = f;
//	stream_open(inode, res[0]);
//	stream_open(inode, res[1]);
//	return 0;
//}

//static int __do_pipe_flags(int *fd, struct file **files, int flags)
//{
//	int error;
//	int fdw, fdr;

//	if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
//		return -EINVAL;

//	error = create_pipe_files(files, flags);
//	if (error)
//		return error;

//	error = get_unused_fd_flags(flags);
//	if (error < 0)
//		goto err_read_pipe;
//	fdr = error;

//	error = get_unused_fd_flags(flags);
//	if (error < 0)
//		goto err_fdr;
//	fdw = error;

//	audit_fd_pair(fdr, fdw);
//	fd[0] = fdr;
//	fd[1] = fdw;
//	return 0;

// err_fdr:
//	put_unused_fd(fdr);
// err_read_pipe:
//	fput(files[0]);
//	fput(files[1]);
//	return error;
//}

//int do_pipe_flags(int *fd, int flags)
//{
//	struct file *files[2];
//	int error = __do_pipe_flags(fd, files, flags);
//	if (!error) {
//		fd_install(fd[0], files[0]);
//		fd_install(fd[1], files[1]);
//	}
//	return error;
//}

///*
// * sys_pipe() is the normal C calling standard for creating
// * a pipe. It's not the way Unix traditionally does this, though.
// */
//static int do_pipe2(int __user *fildes, int flags)
//{
//	struct file *files[2];
//	int fd[2];
//	int error;

//	error = __do_pipe_flags(fd, files, flags);
//	if (!error) {
//		if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
//			fput(files[0]);
//			fput(files[1]);
//			put_unused_fd(fd[0]);
//			put_unused_fd(fd[1]);
//			error = -EFAULT;
//		} else {
//			fd_install(fd[0], files[0]);
//			fd_install(fd[1], files[1]);
//		}
//	}
//	return error;
//}

//SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
//{
//	return do_pipe2(fildes, flags);
//}

//SYSCALL_DEFINE1(pipe, int __user *, fildes)
//{
//	return do_pipe2(fildes, 0);
//}

///*
// * This is the stupid "wait for pipe to be readable or writable"
// * model.
// *
// * See pipe_read/write() for the proper kind of exclusive wait,
// * but that requires that we wake up any other readers/writers
// * if we then do not end up reading everything (ie the whole
// * "wake_next_reader/writer" logic in pipe_read/write()).
// */
//void pipe_wait_readable(struct pipe_inode_info *pipe)
//{
//	pipe_unlock(pipe);
//	wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
//	pipe_lock(pipe);
//}

//void pipe_wait_writable(struct pipe_inode_info *pipe)
//{
//	pipe_unlock(pipe);
//	wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
//	pipe_lock(pipe);
//}

///*
// * This depends on both the wait (here) and the wakeup (wake_up_partner)
// * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
// * race with the count check and waitqueue prep.
// *
// * Normally in order to avoid races, you'd do the prepare_to_wait() first,
// * then check the condition you're waiting for, and only then sleep. But
// * because of the pipe lock, we can check the condition before being on
// * the wait queue.
// *
// * We use the 'rd_wait' waitqueue for pipe partner waiting.
// */
//static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
//{
//	DEFINE_WAIT(rdwait);
//	int cur = *cnt;

//	while (cur == *cnt) {
//		prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
//		pipe_unlock(pipe);
//		schedule();
//		finish_wait(&pipe->rd_wait, &rdwait);
//		pipe_lock(pipe);
//		if (signal_pending(current))
//			break;
//	}
//	return cur == *cnt ? -ERESTARTSYS : 0;
//}

//static void wake_up_partner(struct pipe_inode_info *pipe)
//{
//	wake_up_interruptible_all(&pipe->rd_wait);
//}

//static int fifo_open(struct inode *inode, struct file *filp)
//{
//	struct pipe_inode_info *pipe;
//	bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
//	int ret;

//	filp->f_version = 0;

//	spin_lock(&inode->i_lock);
//	if (inode->i_pipe) {
//		pipe = inode->i_pipe;
//		pipe->files++;
//		spin_unlock(&inode->i_lock);
//	} else {
//		spin_unlock(&inode->i_lock);
//		pipe = alloc_pipe_info();
//		if (!pipe)
//			return -ENOMEM;
//		pipe->files = 1;
//		spin_lock(&inode->i_lock);
//		if (unlikely(inode->i_pipe)) {
//			inode->i_pipe->files++;
//			spin_unlock(&inode->i_lock);
//			free_pipe_info(pipe);
//			pipe = inode->i_pipe;
//		} else {
//			inode->i_pipe = pipe;
//			spin_unlock(&inode->i_lock);
//		}
//	}
//	filp->private_data = pipe;
//	/* OK, we have a pipe and it's pinned down */

//	__pipe_lock(pipe);

//	/* We can only do regular read/write on fifos */
//	stream_open(inode, filp);

//	switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
//	case FMODE_READ:
//	/*
//	 *  O_RDONLY
//	 *  POSIX.1 says that O_NONBLOCK means return with the FIFO
//	 *  opened, even when there is no process writing the FIFO.
//	 */
//		pipe->r_counter++;
//		if (pipe->readers++ == 0)
//			wake_up_partner(pipe);

//		if (!is_pipe && !pipe->writers) {
//			if ((filp->f_flags & O_NONBLOCK)) {
//				/* suppress EPOLLHUP until we have
//				 * seen a writer */
//				filp->f_version = pipe->w_counter;
//			} else {
//				if (wait_for_partner(pipe, &pipe->w_counter))
//					goto err_rd;
//			}
//		}
//		break;

//	case FMODE_WRITE:
//	/*
//	 *  O_WRONLY
//	 *  POSIX.1 says that O_NONBLOCK means return -1 with
//	 *  errno=ENXIO when there is no process reading the FIFO.
//	 */
//		ret = -ENXIO;
//		if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
//			goto err;

//		pipe->w_counter++;
//		if (!pipe->writers++)
//			wake_up_partner(pipe);

//		if (!is_pipe && !pipe->readers) {
//			if (wait_for_partner(pipe, &pipe->r_counter))
//				goto err_wr;
//		}
//		break;

//	case FMODE_READ | FMODE_WRITE:
//	/*
//	 *  O_RDWR
//	 *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
//	 *  This implementation will NEVER block on a O_RDWR open, since
//	 *  the process can at least talk to itself.
//	 */

//		pipe->readers++;
//		pipe->writers++;
//		pipe->r_counter++;
//		pipe->w_counter++;
//		if (pipe->readers == 1 || pipe->writers == 1)
//			wake_up_partner(pipe);
//		break;

//	default:
//		ret = -EINVAL;
//		goto err;
//	}

//	/* Ok! */
//	__pipe_unlock(pipe);
//	return 0;

//err_rd:
//	if (!--pipe->readers)
//		wake_up_interruptible(&pipe->wr_wait);
//	ret = -ERESTARTSYS;
//	goto err;

//err_wr:
//	if (!--pipe->writers)
//		wake_up_interruptible_all(&pipe->rd_wait);
//	ret = -ERESTARTSYS;
//	goto err;

//err:
//	__pipe_unlock(pipe);

//	put_pipe_info(inode, pipe);
//	return ret;
//}

//const struct file_operations pipefifo_fops = {
//	.open		= fifo_open,
//	.llseek		= no_llseek,
//	.read_iter	= pipe_read,
//	.write_iter	= pipe_write,
//	.poll		= pipe_poll,
//	.unlocked_ioctl	= pipe_ioctl,
//	.release	= pipe_release,
//	.fasync		= pipe_fasync,
//	.splice_write	= iter_file_splice_write,
//};

///*
// * Currently we rely on the pipe array holding a power-of-2 number
// * of pages. Returns 0 on error.
// */
//unsigned int round_pipe_size(unsigned long size)
//{
//	if (size > (1U << 31))
//		return 0;

//	/* Minimum pipe size, as required by POSIX */
//	if (size < PAGE_SIZE)
//		return PAGE_SIZE;

//	return roundup_pow_of_two(size);
//}

///*
// * Resize the pipe ring to a number of slots.
// */
//int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
//{
//	struct pipe_buffer *bufs;
//	unsigned int head, tail, mask, n;

//	/*
//	 * We can shrink the pipe, if arg is greater than the ring occupancy.
//	 * Since we don't expect a lot of shrink+grow operations, just free and
//	 * allocate again like we would do for growing.  If the pipe currently
//	 * contains more buffers than arg, then return busy.
//	 */
//	mask = pipe->ring_size - 1;
//	head = pipe->head;
//	tail = pipe->tail;
//	n = pipe_occupancy(pipe->head, pipe->tail);
//	if (nr_slots < n)
//		return -EBUSY;

//	bufs = kcalloc(nr_slots, sizeof(*bufs),
//		       GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
//	if (unlikely(!bufs))
//		return -ENOMEM;

//	/*
//	 * The pipe array wraps around, so just start the new one at zero
//	 * and adjust the indices.
//	 */
//	if (n > 0) {
//		unsigned int h = head & mask;
//		unsigned int t = tail & mask;
//		if (h > t) {
//			memcpy(bufs, pipe->bufs + t,
//			       n * sizeof(struct pipe_buffer));
//		} else {
//			unsigned int tsize = pipe->ring_size - t;
//			if (h > 0)
//				memcpy(bufs + tsize, pipe->bufs,
//				       h * sizeof(struct pipe_buffer));
//			memcpy(bufs, pipe->bufs + t,
//			       tsize * sizeof(struct pipe_buffer));
//		}
//	}

//	head = n;
//	tail = 0;

//	kfree(pipe->bufs);
//	pipe->bufs = bufs;
//	pipe->ring_size = nr_slots;
//	if (pipe->max_usage > nr_slots)
//		pipe->max_usage = nr_slots;
//	pipe->tail = tail;
//	pipe->head = head;

//	/* This might have made more room for writers */
//	wake_up_interruptible(&pipe->wr_wait);
//	return 0;
//}

///*
// * Allocate a new array of pipe buffers and copy the info over. Returns the
// * pipe size if successful, or return -ERROR on error.
// */
//static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
//{
//	unsigned long user_bufs;
//	unsigned int nr_slots, size;
//	long ret = 0;

//#ifdef CONFIG_WATCH_QUEUE
//	if (pipe->watch_queue)
//		return -EBUSY;
//#endif

//	size = round_pipe_size(arg);
//	nr_slots = size >> PAGE_SHIFT;

//	if (!nr_slots)
//		return -EINVAL;

//	/*
//	 * If trying to increase the pipe capacity, check that an
//	 * unprivileged user is not trying to exceed various limits
//	 * (soft limit check here, hard limit check just below).
//	 * Decreasing the pipe capacity is always permitted, even
//	 * if the user is currently over a limit.
//	 */
//	if (nr_slots > pipe->max_usage &&
//			size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
//		return -EPERM;

//	user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);

//	if (nr_slots > pipe->max_usage &&
//			(too_many_pipe_buffers_hard(user_bufs) ||
//			 too_many_pipe_buffers_soft(user_bufs)) &&
//			pipe_is_unprivileged_user()) {
//		ret = -EPERM;
//		goto out_revert_acct;
//	}

//	ret = pipe_resize_ring(pipe, nr_slots);
//	if (ret < 0)
//		goto out_revert_acct;

//	pipe->max_usage = nr_slots;
//	pipe->nr_accounted = nr_slots;
//	return pipe->max_usage * PAGE_SIZE;

//out_revert_acct:
//	(void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
//	return ret;
//}

///*
// * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
// * location, so checking ->i_pipe is not enough to verify that this is a
// * pipe.
// */
//struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
//{
//	struct pipe_inode_info *pipe = file->private_data;

//	if (file->f_op != &pipefifo_fops || !pipe)
//		return NULL;
//#ifdef CONFIG_WATCH_QUEUE
//	if (for_splice && pipe->watch_queue)
//		return NULL;
//#endif
//	return pipe;
//}

//long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
//{
//	struct pipe_inode_info *pipe;
//	long ret;

//	pipe = get_pipe_info(file, false);
//	if (!pipe)
//		return -EBADF;

//	__pipe_lock(pipe);

//	switch (cmd) {
//	case F_SETPIPE_SZ:
//		ret = pipe_set_size(pipe, arg);
//		break;
//	case F_GETPIPE_SZ:
//		ret = pipe->max_usage * PAGE_SIZE;
//		break;
//	default:
//		ret = -EINVAL;
//		break;
//	}

//	__pipe_unlock(pipe);
//	return ret;
//}

//static const struct super_operations pipefs_ops = {
//	.destroy_inode = free_inode_nonrcu,
//	.statfs = simple_statfs,
//};

///*
// * pipefs should _never_ be mounted by userland - too much of security hassle,
// * no real gain from having the whole whorehouse mounted. So we don't need
// * any operations on the root directory. However, we need a non-trivial
// * d_name - pipe: will go nicely and kill the special-casing in procfs.
// */

//static int pipefs_init_fs_context(struct fs_context *fc)
//{
//	struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
//	if (!ctx)
//		return -ENOMEM;
//	ctx->ops = &pipefs_ops;
//	ctx->dops = &pipefs_dentry_operations;
//	return 0;
//}

//static struct file_system_type pipe_fs_type = {
//	.name		= "pipefs",
//	.init_fs_context = pipefs_init_fs_context,
//	.kill_sb	= kill_anon_super,
//};

//static int __init init_pipe_fs(void)
//{
//	int err = register_filesystem(&pipe_fs_type);

//	if (!err) {
//		pipe_mnt = kern_mount(&pipe_fs_type);
//		if (IS_ERR(pipe_mnt)) {
//			err = PTR_ERR(pipe_mnt);
//			unregister_filesystem(&pipe_fs_type);
//		}
//	}
//	return err;
//}

//fs_initcall(init_pipe_fs);
